It is oftentimes necessary to inject a fluid into the body of a patient. For many years, such materials were fed to a patient only by the force of gravity which necessitated placing the container, containing the liquid for delivery to the patient, at a considerable elevation above the patient.
Such devices were not entirely satisfactory in view of the height requirement and difficulty in accurately regulating material flow. Regulation could only be secured by a hand-set tube clasp, and control was secured by counting the drops of fluid in a predetermined time, and then periodically checking by a nurse to determine that the desired rate of delivery was being maintained, because venous dilation changes cause variation in the resistance of flow of I.V. fluids into the body which modifies delivery rate. Gravity flow made it very difficult to maintain a regulated flow over a prolonged period of time.
In recent years, there has been considerable interest in intravenous delivery pumps for the infusion of saline solutions, and the like, to a patient, and there has been a trend toward developing a positive acting pump which could be accurate in its delivery of intravenous fluid medium to the patient, could be readily adjusted, and would be positive in its operation without requiring the placing of the bottle at some distance above the patient. Most pumps heretofore suggested, however, have been rather expensive and, hence, could not be used once and then discarded. Such pumps were difficult to disassemble, sterilize, and reassemble so that sterilization and maintenance of sterile conditions proved to be difficult.
In addition, known pumping devices draw from the intravenous containers and require air to be drawn into the intravenous fluid system to replace the volume of fluid displaced into the body, which can cause either contamination of the fluid from materials and organisms carried in the air or actual pumping of air into the patient's venous system (air embolism), if the pump is not shut off when the intravenous fluid container becomes empty.
The existing methods of allowing air to displace the fluid drawn from the intravenous fluid container system also results in volume delivery highly susceptible to pressure variation, causing variations in volumetric delivery. The extremes in volumetric delivery caused by pressure variation are unwanted and can cause repeated withdrawal and reinjection of the patient's blood or an overly-rapid delivery of fluid to the patient. These extreme cases can cause, respectively, damage to the patient's blood or toxicity from an excessive volume of some intravenous fluids.
Further, pumps of this nature can, under certain circumstances, be installed so that the action is reversed, thereby pumping blood from the patient until (and if) the fault is detected and corrected. Since known pumps operate with an open system, they will continue to pump air or fluid thereby causing either air embolism or draining the patient's blood supply, if not turned off at the appropriate time. Known pumps depend upon sensing means to detect failure modes of the pump, such as pumping air and blockage of the needle site (pressure build-up), and do not preclude the problems because of their inherent design. Such sensing means have been known to fail from time to time.
Prior art devices have heretofore been suggested for controlled liquid dispensing of a fluid in an intravenous solution (see, for example, U.S. Pat. No. 3,967,620), and devices have heretofore been suggested and/or utilized for dispensing of liquids through use of containers having compartments therein with the compartments containing the fluid being collapsed to cause fluid to be discharged therefrom (see, for example, U.S. Pat. Nos. 3,838,794; 3,506,005; 3,731,681; 3,797,492; 3,894,538; 3,756,459; 3,938,539; 3,955,557; and 3,974,825). In addition devices have herefore been suggested and/or utilized for causing a fluid to be dispensed utilizing mechanical means and/or vacuum means (see, for example, U.S. Pat. Nos. 3,884,228 and 3,965,946).